Dead weight display apparatus

ABSTRACT

In accordance with an output signal from a weight sensor mounted on a vehicle, a display control section causes a display unit to display weights calculated at predetermined intervals by a weight calculating section. The display control section adds, to the weight which is being displayed, the difference in the weights sequentially calculated by the weight calculating section from detection of start of a loading/unloading operation performed by a detection section to start of running of the vehicle and causes the display unit to display the obtained weight. When a release detection section has detected release of the brake within a predetermined time from the stoppage of the vehicle, detection of start of a loading/unloading operation is inhibited for a predetermined time from detection of the release. If release of the brake is not detected within a predetermined time from the moment at which the vehicle has been brought to the stoppage state, detection of start of a loading/unloading operation is enabled after a predetermined time elapses from the stoppage of the vehicle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dead weight display apparatus fordisplaying weight loaded on a vehicle, more particularly on a bed of avehicle for carrying cargo so as to prevent an overload.

2. Description of the Related Art

A dead weight display apparatus of the foregoing type has beenstructured such that loads applied to the front and rear wheels of thevehicle are detected by sensors and weight is calculated in accordancewith signals output from the sensors so as to issue an alarm if the deadweight becomes excessive. However, since loads applied to the sensorsare changed during running of the vehicle, an accurate dead weightcannot be displayed. Accordingly, there has been suggested a structurecapable of preventing the foregoing problem in Japanese PatentUnexamined Publication No. Hei. 8-50054.

The dead weight display apparatus suggested as described above has astructure such that the weight calculated in accordance with outputsignals from sensors is not displayed on a display unit as it is duringrunning of the vehicle. As an alternative to this, the weight detectedbefore start of running by a predetermined time is displayed and displayof this weight is retained until another predetermined time elapsesafter running has been stopped. That is, the weight detected beforestart of running by a predetermined time is displayed in a period fromstart of running of the vehicle to a moment at which a predeterminedtime has passed from stoppage of the vehicle. If start of aloading/unloading operation has been detected after a predetermined timehas elapsed from stoppage of the vehicle, the weight calculated inaccordance with output signals from the sensors can be correspondentlydisplayed on the display unit. The weight detected after the vehicle hasbeen stopped does not always coincide with the weight detected beforestart of running of the vehicle even if loading or unloading is notperformed. Therefore, the difference between weights calculatedsequentially is added to the weight displayed previously so as to updatethe display after the vehicle has been stopped.

Incidentally, since a vehicle on which the dead weight display apparatusis mounted has a car body A of the vehicle which is, as shown in FIG.14(a), supported by front and rear wheels, the central portion of abuffer member D made of a leaf spring is secured to an axle portion C ofeach wheel B. Moreover, the two longitudinal ends are rotativelyconnected to two portions in the bottom of the car body by supportshafts E1 and E2. Sensors S for detecting loads respectively added tothe front and rear wheels of the vehicle are usually accommodated andattached in the support shafts for rotatively connecting one of the twolongitudinal ends of the buffer member to the bottom portion of the carbody as shown in FIG. 14(a). The sensors for the front wheels areattached to the rear support shaft E2 and those for the rear wheels areattached to the front support shaft E1.

In the above-mentioned structure, weights of the car body A and thecargo are shared and added to the respective wheels. For example, thefront wheel bears reaction force F having the magnitude corresponding tothat of a load added to the wheel B from the portion adjacent to theground, as shown in FIG. 14(a). The reaction force F is shared by thesupport shafts E1 and E2 at the two longitudinal ends of the buffermember D. When a driver applies the foot to the brake pedal to stop therunning vehicle and the vehicle is thus stopped in a state where thefoot is applied to the brake pedal, a state is realized in which forceF2 borne by the rear support shaft E2 of the buffer member D is made tobe larger than force F1 borne by the front support shaft E1 of the same.

If the above-mentioned state is realized, the sensor S accommodated inthe rear support shaft E2 detects weight heavier than the weight whichmust be detected. However, the foregoing fact does not raise a problemin a state where the brake is not released, that is, the brake isoperated.

If the brake is released or moderated after the vehicle has beenstopped, the deviated force is released so that force F1' borne by thefront support shaft E1 at one of the two ends of the buffer member D andforce F2' borne by the rear support shaft E2 are gradually changed so asto be substantially equal to each other, as shown in FIG. 14(b).Therefore, the weight which is detected by the sensor S accommodated inthe rear support shaft E2 is gradually changed from heavy weightdetected before the brake is released to light weight.

Therefore, if the brake is released or moderated before a predeterminedtime elapses from stoppage of the vehicle, the weight which is detectedby the sensor S is changed instably. If an operation for detecting startof a loading/unloading operation is performed in the above-mentionedperiod, weights sequentially calculated in accordance with outputsignals from the sensors which are changed even if no loading/unloadingoperation is performed becomes different. The difference in weight isadded to the previously displayed weight to update the display.Therefore, even if a loading/unloading operation is not actuallyperformed, display as if the weight has been reduced is performed on thedisplay unit.

The weight displayed on the display unit is used as a reference value ofthe weight which is enlarged or reduced attributable to the afterwardloading/unloading operation. If the weight is enlarged attributable tothe afterward loading operation, smaller weight is displayed. Accordingto circumstances, display does not reflect an overload. The overloadstate cannot be determined and thus an alarm cannot be issued.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a dead weight display apparatus improved to be capable ofdisplaying accurate dead weight.

In order to achieve the above-mentioned object, the invention provides adead weight display apparatus which comprises a weight calculating meansfor calculating a weight at regular intervals in response to an outputsignal from a sensor attached to a vehicle and display means fordisplaying the weight. Display control means control the display meansto display the weight calculated by the weight calculating means anddetection means detect the start of a loading/unloading operation.Release detection means detect the release of a brake of the vehicle,wherein the display control means adds a difference between the weightssequentially calculated by the weight calculating means from detectionof start of the loading/unloading operation performed by the detectionmeans to start of running of the vehicle to the weight which is beingdisplayed and causes the display means to display the added weight.

When the release detection means detects release of the brake during atime period which is count down by a time, beginning with a moment atwhich the running vehicle has been brought to a stoppage state,detection of start of a loading/unloading operation which is performedby the detection means is inhibited for the predetermined time from thedetection of the release of the brake, and when the release detectionmeans does not detect release of the brake within the predetermined timefrom the moment at which the running vehicle has been brought to astoppage state, detection of start of a loading/unloading operationwhich is performed by the detection means is enabled after thepredetermined time elapses from the stoppage of the vehicle.

Thus, the timer disables or inhibits the performance of the detectionmeans until the timer counts down a predetermined time. The timerrestarts the countdown if the brake is released before the timer reacheszero.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a basic structural view showing a dead weight displayapparatus according to the present invention.

FIG. 2 is a block diagram showing an embodiment of the dead weightdisplay apparatus according to the present invention.

FIG. 3 is a block diagram showing an example of a weight sensor to beapplied to the structure shown in FIG. 2 and illustrating a specificexample of a sensor and a V/F conversion section.

FIG. 4 is a flow chart showing an example of a main routine of theprocess which is performed by a CPU shown in FIG. 2.

FIG. 5 is a flow chart showing an interruption process which isperformed by the CPU in the μCOM shown in FIG. 2.

FIG. 6 is a flow chart showing another interruption process which isperformed by the CPU in the μCOM shown in FIG. 2.

FIG. 7 is a diagram showing a timer in the form of a timer group in theμCOM shown in FIG. 2.

FIG. 8 is a diagram showing various areas formed in the work area in anRAM in the μCOM shown in FIG. 2 for use to execute the process in theflow charts shown in FIGS. 4 to 6.

FIG. 9 is an explanatory view of a specific process which is performedin accordance with the flow chart shown in FIG. 4.

FIG. 10 is a flow chart showing another example of the main routine ofthe process which is performed by the CPU in the μCOM shown in FIG. 2.

FIG. 11 is a diagram showing various areas formed in the work area inthe RAM in the μCOM shown in FIG. 2 for use to execute the process inthe flow chart shown in FIG. 10.

FIG. 12 is a diagram showing a problem which must be overcome when theprocess in the flow chart shown in FIG. 10 is performed.

FIGS. 13(a) and 13(b) are diagrams showing methods for overcoming theproblem shown in FIG. 12.

FIGS. 14(a) and 14(b) are explanatory views for explaining problemsexperienced with the conventional technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A dead weight display apparatus according to the present invention, asshown in FIG. 1 which is a basic structural view, comprises a weightcalculating section 101a for calculating weight at regular intervals inresponse to output signals from a sensor 111 attached to a vehicle; adisplay section 13 for displaying the weight; a display control section101b for controlling the display section to display the weightcalculated by the weight calculating section; and a detection section101c for detecting start of a loading/unloading operation. Further, thedead weight display apparatus is arranged such that the display controlsection adds difference between the weights sequentially calculated bythe weight calculating section from detection of start of theloading/unloading operation performed by the detection section to startof running of the vehicle to the weight which is being displayed andcauses the display section to display the added weight, wherein arelease detection section 101d for detecting release of a brake isfurther provided, and when the release detection section detects brakerelease within a predetermined time from a moment at which the runningvehicle has been brought to a stoppage state, detection of start of aloading/unloading operation which is performed by the detection sectionis inhibited for the predetermined time from the detection of the brakerelease, and when the release detection section does not detect brakerelease within the predetermined time from the moment at which therunning vehicle has been brought to the stoppage state, the detection ofstart of a loading/unloading operation which is performed by thedetection section is enabled after the predetermined time elapses fromthe stoppage of the vehicle.

In the above-mentioned structure, the display control section 101bperforms a control to cause the display unit 13 to display the weightscalculated by the weight calculating section 101a at predeterminedintervals in accordance with output signals from the weight sensor 111attached to the vehicle. The display control section adds the differencein the weights sequentially calculated from detection of start of aloading/unloading operation performed by the detection section 101c tostart of running of the vehicle to the weight which is being displayedand causes the display unit to display the added weight. When therelease detection section 101d has detected brake release within apredetermined time from a moment at which the running vehicle has beenstopped, detection of start of a loading/unloading operation which isperformed by the detection section is inhibited for the predeterminedtime from the detection of the brake release. If the release detectionsection does not detect brake release within the predetermined time fromthe moment at which the running vehicle has been brought to the stoppagestate, the detection section is enabled to detect start of aloading/unloading operation after the predetermined time has elapsedfrom the moment at which the vehicle has been brought to the stoppedstate.

Therefore, even if the brake is released before a predetermined timeelapses from a moment at which the vehicle has been brought to thestoppage state, start of a loading/unloading operation is not detectedfor a predetermined time from the brake release. Thus, the differencebetween weights sequentially calculated in accordance with outputsignals from the sensor which are changed when the brake has beenreleased is not added to the weight which is being displayed and thusdisplay on the display unit is not updated.

An embodiment of the present invention will now be described withreference to FIGS. 2 to 5. FIG. 2 is a diagram showing an embodiment ofa dead weight display apparatus according to the present invention. Thedead weight display. apparatus, as shown in FIG. 2, has a one-chipmicrocomputer (μCOM) 10 arranged to be operated with electric powersupplied from a power supply circuit which will be described later. Arunning-sensor signal input terminal I and load-sensor signal inputterminals I1 to In are, through an interface (I/F) circuit 11, connectedto the μCOM 10. The running-sensor signal input terminal I is suppliedwith running pulses from a running sensor (not shown), while theload-sensor signal input terminals I1 to In are supplied with pulseshaving a frequency in proportion to voltage output from a weight sensorwhich will be described later.

As the weight sensor, a sensor having a structure shown in FIG. 3 isemployed. The weight sensor has a sensor 111 and a V/F conversionsection 112 and is structured to be operated with electric powersupplied from a power supply circuit which will be described later. Thesensor 111 has a magnetostrictor 111a and a transformer 111b, themagnetic path of which is the magnetostrictor 111a. The V/F conversionsection 112 has an oscillator 112a, a resistor 112b, a wave detector112c and a V/F conversion circuit 112d. When a load is applied to themagnetostrictor 111a, distortion is generated, thus causing the magneticpermeability to be changed. If the magnetic permeability is changed,voltage induced by a secondary coil of the transformer 111b is changed.

The voltage induced by the secondary coil is converted into a directcurrent (DC) by the wave detector so that the V/F conversion circuit112d outputs a pulse signal having a frequency which is in proportion tothe DC voltage. Note that the resistor 112b is a resistor having a largeresistance value so as to be capable of maintaining an electric currentwhich flows in a primary coil of the transformer 111b even if the outputfrom the oscillator 112a is somewhat changed.

The wave detector 112c performs multiplication wave detection of theoutput signal from the secondary coil of the transformer 111b and asignal generated in the resistor 112b to reduce mixed noise components.The sensor 111 is provided for each of, for example, brackets for fixingthe chassis and springs to which the weight of the vehicle istransmitted to the front wheels and the rear wheels. When a load isadded to the sensor 111, the weight sensor causes the V/F conversionsection 112 to output a pulse signal having a frequency corresponding tothe added weight. The weight sensors include a type having therelationship between the weight and the frequency which is changedlinearly and a type having the relationship between the same which ischanged non-linearly in accordance with the characteristics of theweight sensor 111 and the V/F conversion section 112.

The μCOM 10 includes a central processing unit (CPU) 101 arranged to beoperated in accordance with a program, a ROM 102 storing programs andstationary data, a RAM 103 having a data area for storing various dataitems and a work area which is used by the CPU 101 for performing aprocess, and a timer group 104 serving as a time measuring means formeasuring various time periods. The CPU 101 performs a process arrangedas shown in a flow chart which will be described later to serve as theweight calculating section 101a, the display control section 101b, thedetection section 101c and the power supply control section 101d asdescribed with reference to the basic structural view shown in FIG. 1.

A switch group 12 is connected to the μCOM 10, and a display unit 13serving as a display means is connected to the same. The switch group 12includes key switches serving as an input means for inputting variousdata items and detection switches for detecting various states. As oneof the detection switches, a brake switch is provided. The display unit13 is operated with electric power supplied from the power supplycircuit which will be described later. Moreover, a nonvolatile memory(NVM) 14 storing data in such a manner that data cannot be lost even ifelectric power is not supplied, an ignition (IGN) switch 16 through aninterface (I/F) circuit 15, and signal output terminals O and O1 to Onthrough an interface (I/F) circuit 17 are connected to the μCOM 10respectively.

The signal output terminal O outputs dead weight W obtained by addingthe weight calculated in accordance with the load sensor signalssupplied to the signal input terminals I1 to In. The signal outputterminals O1 to On respectively output weights W1 to Wn calculated inaccordance with the weight sensor signals supplied to the signal inputterminals I1 to In. Reference numeral 18 designates a power supplycircuit structured to supply electric power to the units including theμCOM 10 in the apparatus and is supplied with electric power from abattery 19 mounted on the vehicle. The power supply from the powersupply circuit 18 to the weight sensors and the display unit 13 iscontrolled by the CPU 101 of the μCOM 10.

Note that the weight of the vehicle must be omitted in order to displaythe weight loaded on the vehicle on the display unit 13. Thus, theweight sensor 111 is mounted on the vehicle, and then the frequencyoutput from the V/F conversion section 112 in a state where no cargo isloaded is measured so as to be recorded in a weight conversioncoefficient recording portion of the nonvolatile memory 14. Weightvalues corresponding to the respective sensors and serving as referenceswith which overload is determined and weight values serving as areference with which overload of the overall weight loaded on thevehicle is determined are previously provided and stored in an overloadweight recording portion of the nonvolatile memory 14. Data recorded inthe nonvolatile memory 14 is retained even if the power supply is turnedoff.

The CPU 101 of the μCOM 10 performs a data setting process for recordingdata input from the switch group 12 in the weight conversion coefficientrecording portion and the overload weight recording portion of thenonvolatile memory 14. The CPU 101 measures the frequencies of the pulsesignals supplied from load sensors (not shown) through the I/F 11 andreceived by the input terminals I1 to In. That is, a calculationexpressed by the following equation (1) is performed so that frequency His calculated:

    Hi=Ni/To                                                   (1)

wherein Hi is the frequency of the i-th sensor, To is a predeterminedtime (seconds) and Ni is the number of pulses of the i-th sensor whichare output in To seconds.

If the frequency calculated in accordance with the foregoing equation(1) is not included in a predetermined range, occurrence of an error isdisplayed by the display unit 13. If a value, which is not realizedusually, is measured attributable of mixture of noise or the like,occurrence of an error is displayed and the value is omitted.

The CPU 101 of the μCOM 10 determines whether or not a pulse signal hasbeen, through the I/F 11, supplied from a running sensor mounted on thevehicle in a predetermined measuring period for a predetermined-timetimer of the timer group 104 in the μCOM 10 so as to determine whetherthe vehicle is being driven or stopped.

The CPU 101 of the μCOM 10 reads a conversion coefficient and an offsetfrequency value from the weight conversion coefficient recording portionof the nonvolatile memory 14 to calculate the weight in accordance withthe following equation (2):

    Wi=Ki(H-HO)                                                (2)

wherein Ki is the weight conversion coefficient of the i-th sensor, HOis the offset frequency value of the i-th sensor and H is the frequencyof the i-th sensor. The weights calculated in accordance with equation(2) and added to the respective weight sensors are added in accordancewith the following equation (3) so as to calculate the dead weight W:

    W=W1+W2+, . . . , +Wn                                      (3)

Weight Wi calculated in accordance with equation (2) and added to eachweight sensor and dead weight W calculated in accordance with equation(3) are output through the I/F 17. Moreover, the dead weight W isdisplayed on the display unit 13. Data output through the I/F 17 isrecorded on a connected recording apparatus if necessary so as to beused to administrate the state of operation of the vehicle.

The CPU 101 of the μCOM 10 determines whether or not the weightcalculated in accordance with the equations (2) and (3) is the overloadweight by making a reference to data recorded in the overload weightrecording portion of the nonvolatile memory 14. If overload isdetermined, a buzzer (not shown) is operated and occurrence of theoverload is displayed on the display unit 13. If the overload isdetermined, information of the overload of the weight loaded on eachweight sensor and the dead weight is output through the I/F 17.

The operation of this embodiment will now be described with reference toflow charts shown in FIGS. 4 to 6 showing the processes which areperformed by the CPU 101 of the μCOM 10. In this embodiment, the switchgroup 12 is provided with a loading/unloading switch composed of amomentary switch for generating a signal when depressed, and also abrake switch (not shown) for generating an on/off signal in accordancewith the brake pedal. The timer group 104 is, as shown in FIG. 7,composed of a two-second timer 4a, a six-second timer 4b and a5-60-minute timer 4c. The flow chart of the main routine which isperformed by the CPU 101 and shown in FIG. 4 is executed when theignition (IGN) switch 16 of the vehicle having the apparatus mountedthereon is first switched on.

In step S101 initialization is performed so that the contents of an HFflag area 3a, a KF flag area 3b, a BF flag area 3bb, an SP flag area 3c,an HKF flag area 3d, an area 3e for weight W1 calculated this time, anarea 3f for previously calculated weight W2 and an area 3g for displayedweight WD formed in the work area in the RAM 103 and shown in FIG. 8 arereset. Moreover, initial display of the display unit 13 is set to bezero ton.

Note that the HF flag area 3a is made to be 0 whenever the two-secondtimer 4a included in the timer group 104 measures two seconds. If apulse signal is supplied to the running-sensor signal input terminal Iwhen the HF flag area 3a is 0, the HF flag area 3a is made to be 1. TheKF flag area 3b is made to be 1 whenever the six-second timer 4bincluded in the timer group 104 starts to measure six seconds, while thesame is made to be 0 when the six-second timer completes measurement ofsix seconds. The SP flag area 3c is made to be 0 immediately before thetwo-second timer 4a starts the measurement. If a pulse signal issupplied to the running-sensor signal input terminal I when the HF flagarea 3a is 0, the SP flag area 3c is made to be 1.

When the CPU 101 of the μCOM 10 receives the pulse signal input to therunning-sensor signal input terminal I through the interface (I/F)circuit 11, it executes a pulse interruption routine process shown inFIG. 5. When operation of the loading/unloading switch has been input,it executes a loading/unloading switch interruption routine processshown in FIG. 6.

The pulse interruption routine process which is started when a pulsesignal has been supplied to the running-sensor signal input terminal Iis performed such that whether or not the HF flag area 3a is 1, that is,whether or not a pulse signal has been supplied within two seconds orrecently. If determination of this process is performed to be NO, theoperation proceeds to step S212 so that the SP flag area 3c is made tobe 1, and then the operation proceeds to step S213. In step S213 the HFflag area 3a is made to be 1, and then the operation returns to the mainroutine shown in FIG. 4. If the determination in step S211 is performedto be YES, that is, if a pulse signal has been supplied within twoseconds or recently, the operation jumps over steps S212 and S213 andreturns to the main routine.

In the loading/unloading switch interruption routine which is startedwhen the loading/unloading switch has been switched on, whether or notthe HKF flag area 3d is 1 in the first step S311 is determined. If thedetermination is performed to be YES, the operation proceeds to stepS312. If the determination is performed to be NO, the operation returnsto the main routine shown in FIG. 4. In step S312 whether or not the KFflag area 3b is 0 is determined. If the determination is performed to beYES, the operation proceeds to step S313. If the determination isperformed to be NO, the operation returns to the main routine shown inFIG. 4. In step S313 the HKF flag area 3d is made to be 0, and then theoperation returns to the main routine shown in FIG. 4. Thus, theoperation of the loading/unloading switch causes the HKF flag area 3d tobe 0.

In the next step S102, whether or not the ignition (IGN) switch 16 hasbeen switched on is determined in accordance with a status signal of theIGN switch 16 supplied through the interface (I/F) circuit 15. If theIGN switch 16 has been switched on and thus the determination in stepS102 is performed to be YES, an ON control signal is output to the powersupply circuit 18 in the next step S103 so as to cause the power supplycircuit 18 to supply electric power to the weight sensor through the I/Fcircuit 11 and also electric power to the display unit 13. If thedetermination in step S102 has been performed to be NO, that is, if theIGN switch 16 has been switched off, the operation proceeds to step S104so that an OFF control signal is output to the power supply circuit 18so as to cause the power supply circuit 18 to interrupt supply ofelectric power to the weight sensor and the display unit 13 through theI/F circuit 11.

After step S104 has been performed, the operation proceeds to step S105so that the 5-60-minute timer 4c is caused to start the measurement of,for example, 10 minutes. In next step S106 completion of the measurementof, for example, 10 minutes from start of the measurement of the5-60-minute timer 4c in step S105 is waited for. If, for example, 10minutes has elapsed from the start of the measurement of the 5-60-minutetimer 4c, the operation proceeds to step S103 so that the ON controlsignal is output to the power supply circuit 18 to cause the powersupply circuit 18 to supply electric power to the weight sensor throughthe I/F circuit 11 and also to supply electric power to the display unit13.

As a result of execution of steps S102 to S106, the CPU 101 serves asthe power supply control section 101d for controlling the power supplycircuit 18. The power supply control section 101d controls to interruptsupply of operating electric power from the power supply circuit 18 whenthe ignition switch 16 is switched off and has a 10-minute timer 4c forrepeatedly measuring predetermined time intervals. Whenever the10-minute timer 4c measures the predetermined time, the power supplycircuit 18 is caused to supply operating electric power to at least thesensors and the CPU.

In the next step S107 the SP flag area 3c in the work area is made to be0. In the next step S108 a time measuring operation of the two-secondtimer 4a which is a display updating timer is started. In the next stepS109 weight sensor signals from the weight-sensor signal input terminalsI1 to In supplied through the I/F circuit 11 are detected. As a resultof the detection, the frequency is obtained in accordance with thenumber of pulses which are supplied in unit time T0 as expressed inequation (1).

In step S110 the dead weight W is calculated in accordance with theforegoing equations (2) and (3). In the next step S111 the consents ofthe area 3e for weight W1 calculated this time are stored in the area 3ffor previously calculated weight W2. In the next step S112 the deadweight W calculated in step S110 is stored in the area 3e for weight W1calculated this time. Then, the operation proceeds to step S113 so thatwhether or not the two-second timer 4a started in step S108 has measuredtwo seconds is determined. Then, waiting for the determination to be YESis performed.

As a result of the above-mentioned steps S108 to S110, the CPU 101 actsas the weight calculating section 101a for calculating the weight atregular intervals in response to the output signal from the weightsensor 111 mounted on the vehicle.

When the two-second timer 4a started in step S108 has measured twoseconds and thus the determination in step S113 has been made to be YES,the operation proceeds to step S114 so that the HF flag area 3a is madeto be 0. Then, the operation proceeds to step S115. In step S115 whetheror not the SP flag area 3c is 1 is determined. That is, whether or not apulse signal has been supplied to the running-sensor signal inputterminal I within two seconds or more recently is determined. If thedetermination in step S105 has been performed to be NO, that is, nopulse signal has been supplied to the running-sensor signal inputterminal I within two seconds or more recently, the operation proceedsto step S116. If the determination has been performed to be YES, thatis, if a pulse signal has been supplied to the running-sensor signalinput terminal I within two seconds or more recently, the operationproceeds to step S117.

In step S117 the HKF flag area 3d is made to be 1, and then theoperation proceeds to step S118 so that the six-second timer 4b startsmeasuring time. In next step S119 the KF flag area 3b is made to be 1,and then the operation proceeds to step S120a so that whether or not theBF flag area 3bb is 1 is determined. If the BF flag area 3bb is 0 andthe determination in step S120a has been performed to be NO, theoperation proceeds to step S120.

In step S120 whether or not the state of the brake switch input from theswitch group 12 is OFF is determined. If the brake switch is switchedoff and the determination has been performed to be YES, that is, if thebrake has been released, the operation proceeds to step S120b so thatthe BF flag area 3bb is made to be 1. Then, the operation proceeds tostep S118 so that the six-second timer 4b restarts measurement of time.

If the brake switch is not switched off, that is, if the determinationin step S120 has been performed to be NO, that is, if the brake has notbeen released, the operation proceeds to step S121. In step S121 whetheror not the six-second timer 4b started in step S118 has measured sixseconds is determined. If the determination in step S121 has beenperformed to be NO, the operation returns to step S102. If thedetermination has been performed to be YES, both of the KF flag area 3band the BF flag area 3bb are made to be 0 in step S122. Then, theoperation returns to step S102.

In step S116 whether or not the KF flag area 3b is 0, that is, whetheror not the six-second timer 4b is measuring time is determined. If thedetermination in step S116 has been performed to be NO, that is, if thesix-second timer 4b is measuring time, the operation proceeds to stepS120. If the determination has been performed to be YES, that is, if theKF flag area 3b indicating an elapse of six seconds from stoppage of thevehicle is 0, the operation proceeds to step S123 so that whether or notthe HKF flag area 3d is 0 is determined. If the HKF flag area 3d is 1and the determination in step S123 is NO, that is, if theloading/unloading switch has not been operated though six seconds haselapsed from stoppage of the vehicle, the operation returns to stepS102.

As described above, whether or not the brake switch is switched off,that is, whether or not the brake has been released is determined instep S120. If the brake has not been released and the predetermined timeof six seconds has elapsed in the foregoing state, both of the KF flagarea 3b and the BF flag area 3bb are made to be 0. If the brake has beenreleased though the predetermined time of six seconds has not elapsed,both of the KF flag area 3b and the BF flag area 3bb are made to be 0after another predetermined time of six seconds has elapsed from theabove-mentioned moment. Therefore, influence of the change in the weightadded to each weight sensor immediately after the brake has beenreleased can be eliminated when the following process is performed.

As a result of execution of the foregoing steps S120, S120a and S120b,the CPU 101 serves as the release detection section 101d for detectingrelease of the brake. When break release is detected within apredetermined time from a moment at which the running vehicle has beenstopped, detection of start of a loading/unloading operation isinhibited for a predetermined time from detection of the brake release.If brake release is not detected within a predetermined time from themoment at which the running vehicle has been stopped, detection of startof a loading/unloading operation is enabled after a predetermined timehas elapsed from the moment at which the vehicle has been stopped.

If the HKF flag area 3d is 0 and thus the determination in step S123 isYES, that is, if six seconds has elapsed from stoppage of the vehicleand the loading/unloading switch has been switched on, the operationproceeds to step S124. In step S124 new weight WD to be displayed iscalculated by adding the difference in the contents of the area 3e forweight W1 calculated this time and the area 3f for previously calculatedweight W2 to the contents to the area 3g for displayed weight WD. Thenewly calculated weight WD is, in the next step S125, output to thedisplay unit 13. In the next step S126 it is stored in the area 3g fordisplayed weight WD in place of the previous weight, and then theoperation returns to step S102.

As a result of the execution of the loading/unloading interruptionswitch routine shown in FIG. 6 and that of step S123, the CPU 101 actsas the detection section 101c for detecting start of theloading/unloading operation. As a result of the execution of steps S124and S125, the CPU 101 acts as the display control section 101b forperforming control to cause the display unit 13 to display thecalculated weight and to cause the display unit 13 to display a resultof addition of the difference in the weights calculated sequentially tothe weight which is being displayed.

As a result of the execution of the foregoing flow chart, weight sensorsignals supplied to the weight-sensor signal input terminals I1 to In inabout first 0.5 second at intervals of two seconds are detected in stepS109 as shown in FIG. 9. In accordance with the detected weight sensorsignals, the dead weight W is calculated in the following step S110. Ifthe pulse interruption routine shown in FIG. 5 is performed at anarbitrary moment during the two seconds, steps S116 and S120 to S126 arenot performed after a lapse of two seconds. Therefore, display of thedead weight W calculated in step S110 is not performed on the displayunit 13.

As a result of the process shown in FIG. 9, apparent enlargement of thedead weight can be deleted which is attributable to a sinking phenomenonof the rear portion of the bed of the vehicle occurring in a period fromtransmission of the power to actual running of the vehicle because of astate in which the wheels are not rotated at the initial stage of startof running of the vehicle and the weight is changed in a state where norunning pulse is supplied, that is, the wheels do not rotate and thusthe vehicle does not run until the power exceeds the initial load evenif power is transmitted to the wheels attributable to the initial load.

Therefore, when a running pulse has been actually supplied from therunning sensor, display of the dead weight W calculated within apredetermined previous time is not performed on the display unit 13.Thus, even if a state is realized in which the weight is changed in astate where the wheels are not rotated and thus no running pulse issupplied, display of the changed dead weight on the display unit canreliably be prevented.

The execution of steps S123 to S126 causes the difference in the weightscalculated every two seconds to be obtained if a loading/unloadingoperation is performed after the loading/unloading switch has beenoperated so as to add the enlargement or reduction in the weight to theweight which is being displayed. Thus, even if the weight is changedduring stopping attributable to a state of stopping, a true weightregardless of the change can continuously be displayed on the displayunit 13.

If steps S123 to S126 are not performed and even if a determination isperformed that the vehicle is stopped in a case where the running pulseis not supplied for time TW (=six seconds) or longer and the weight iscalculated and the calculated weight is displayed, change in thecalculated weight occurring due to the state of the road on which thevehicle is stopped cannot be prevented. Thus, there arises a problem inthat the displayed weight, which is updated whenever stopping for timeTW or longer is performed, becomes different from the weight calculatedand displayed immediately after loading is performed. The execution ofsteps S123 to S126 is able to overcome the foregoing problem.

The operation in the flow charts shown in FIGS. 4 to 6 will now bedescribed in which the loading/unloading switch is operated after alapse of a predetermined time from stoppage of the vehicle, and then theignition switch 16 is switched off without an actual loading/unloadingoperation, and then a loading/unloading operation is performed in astate where the ignition switch 16 is switched off.

When a predetermined time has elapsed from stoppage of the vehicle, norunning pulse is supplied. As a result of step S107 performed at everytwo seconds, the SP flag area 3c is made to be 0. Step S122 causes bothof the KF flag area 3b and the BF flag area 3bb to be 0. When thedetermination in step S115 is NO and the determination in the followingstep S116 is YES, the operation proceeds to step S123. When theloading/unloading switch is operated in the above-mentioned state, theloading/unloading switch interruption process shown in FIG. 6 isperformed so that the HKF flag area 3d is made to be 0 in step S313.When the HKF flag area 3d has been made to be 0, the determination instep S123 is made to be YES so that steps S124 to S126 are performed. Ifno loading/unloading operation is performed in the above-mentionedstate, display on the display unit 13 is not changed.

When the ignition switch 16 is switched off in a state where noloading/unloading operation is performed as described above, thedetermination in step S102 is made to be NO so that an OFF controlsignal is output to the power supply circuit 18 in step S104 tointerrupt supply of electric power to the respective portions. Then, theoperation proceeds to step S105 so that the 10-minute timer 4c isstarted and then the operation proceeds to step S106 so that an elapseof 10 minutes from the timer start is waited for. Note that the periodof 10 minutes is the shortest time taken from switching the IGN switch16 off to completion of the started loading/unloading operation. It maybe made to be a longer time. When the determination in step S106 is madeto be YES after an elapse of 10 minutes, the operation proceeds to stepS103 so that an ON control signal is output to the power supply circuit18 so that electric power is supplied to each portion. Then, steps S107to S116 are performed, and then steps S123 to S126 are performed. Then,the operation returns to S102 so that the foregoing operation isrepeated at intervals of 10 minutes. Since the foregoing repeatedoperation is performed such that electric power is supplied to eachportion in a moment, electric power consumption can be minimized. Thus,complete consumption of the battery can be prevented.

If weights calculated sequentially become different attributable to theloading/unloading operation during the above-mentioned repeatedoperation, the difference is added to the weight which is beingdisplayed so as to update the displayed weight WD. Since no electricpower is supplied to the display unit 13 at this time, display isretained to be turned off. When the ignition switch 16 is switched on,an accurate dead weight enlarged or reduced attributable to theloading/unloading operation can be displayed on the display unit 13.

The foregoing operation is performed in the case where theloading/unloading switch has been switched on and thus the fixed displayof the weight has been suspended when the ignition switch 16 is switchedoff. If the loading/unloading switch has not been switched on when theignition switch 16 is switched off, the HKF flag area 3d does not haveopportunity in which it is made to be 0. In this case, the dead weightwhich is enlarged or reduced attributable to the loading/unloadingoperation cannot be displayed on the display unit 13 in a state wherethe ignition switch 16 is retained to be switched off.

In the above-mentioned embodiment described with reference to the flowcharts shown in FIGS. 4 to 6, the loading/unloading switch must beoperated prior to performing the loading/unloading operation. If it isnot operated, the weight loaded or unloaded from stoppage of the vehicleto the operation of the loading/unloading switch is not added to thedisplayed weight. Thus, enlargement or reduction in the weight cannot bedetected at an intermediate moment, thus causing a state to arise inthat the real dead weight cannot be detected. In this case, the weightdisplay unit does not serve as a required weight display unit. In thiscase, there arises a problem in that all of the cargoes must be unloadedand then reloaded to calculate the actual dead weight.

Another embodiment structured to be capable of solving theabove-mentioned problem will now be described with reference to FIGS. 10and 11.

The hardware structure of this embodiment may be the same as that of thedead weight display apparatus shown in FIG. 2 except for a switch group12 which is not required to be provided with the loading/unloadingswitch. Since the loading/unloading switch is excluded, theloading/unloading switch interruption routine shown in FIG. 6 isomitted. Note that the RAM 103 included in the CPU 101 has, as shown inFIG. 11, an area 3h for reference weight WS and an area 3i for deviationΔW formed in addition to the areas 3a to 3g shown in FIG. 8.

In an initial process set in the first step S101 in the flow chart shownin FIG. 10, the area 3h for reference weight WS is reset and apredetermined value, for example, 0.1 ton to 1 ton, is set to the area3i for deviation ΔW. Steps S102 to S126 are the same as those shown inFIG. 4. However, if the determination in step S121 is performed to beYES, the operation proceeds to step S131 so that weight W1 calculated instep S110 and stored in the area 3e for weight W1 calculated this timein step S112 is stored in the area 3h for reference weight WS. As aresult, the weight W calculated immediately before a lapse of sixseconds from stopping is used in the following process as the referenceweight WS for the stoppage state.

When the determination in step S116 has been performed to be YES, thatis, when six seconds have elapsed, the operation proceeds to step S123so that whether or not the HKF flag area 3d is 0 is determined. Sincethe HKF flag area 3d is retained to be 1 in step S117, the determinationin step S123 is performed to be NO. Then, the operation proceeds to stepS132. In step S132, whether or not the absolute value of the differencebetween the contents of the area 3e for weight W1 calculated this timeand those (=WS) of the area 3h for reference weight WS is equal to thecontents of the area 3i for deviation ΔW or more, that is, whether ornot ΔW≦|W1-W2| is satisfied is determined. This determination isperformed in order to judge whether or not a loading/unloading operationhas been started in accordance with whether or not the weight in thestoppage state has been enlarged or reduced by ΔW or more. If thedetermination has been performed to be NO, the operation returns to stepS102. If the determination has been performed to be YES, the operationproceeds to step S133 so that the contents of the area 3h for referenceweight WS are stored in the area 3h for reference weight WS. Then, inthe next step S134 the HKF flag area 3d is made to be 0, and then theoperation returns to step S102.

As described above, the HKF flag area 3d is made to be 0 in step S134 sothat the determination in step S123 is performed to be YES in a statewhere the vehicle is stopped. Thus, steps S124 to S126 are performed. Asa result, the weights enlarged or reduced attributable to theloading/unloading operation in the stoppage state are sequentially addedor subtracted with respect to the weight which is being displayed sothat the display is updated.

The operation in the flow chart shown in FIGS. 10 and 11 will now bedescribed which is performed when the ignition switch 16 is switched offin a state where no actual loading/unloading operation is performedafter a predetermined time has elapsed from stoppage of the vehicle, andthen the loading/unloading operation is performed in a state where theignition switch 16 is retained to be switched off.

If a predetermined time has elapsed after the vehicle has been stopped,no running pulse is supplied. As a result of step S107 which isperformed at every two seconds, the SP flag area 3c is made to be 0. Instep S122 both of the KF flag area 3b and the BF flag area 3bb are madeto be 0. The determination in step S115 is performed to be NO, and thenthe determination in step S116 is performed to be YES so that theoperation proceeds to step S123. Since the HKF flag area 3d is retainedto be 1 in step S117, the determination in step S123 is performed to beNO so that the operation proceeds to step S132. In step S132 whether ornot a loading/unloading operation has been started is determined inaccordance with whether or not the weight in the stoppage state has beenenlarged or reduced by ΔW or more. If the determination has beenperformed to be NO, the operation returns to step S102 so that the stepsfollowing step S102 are performed.

If the ignition switch 16 is switched off during the above-mentionedprocess without performing a loading/unloading, the determination instep S102 is made to be NO so that the OFF control signal is output tothe power supply circuit 18 in step S104 to interrupt supply of electricpower to each portion. Then, the operation proceeds to step S105 so thatthe 10-minute time 4c is started. Then, the operation proceeds to stepS106 so that an elapse of 10 minutes from start of the timer is waitedfor. When 10 minutes have elapsed and the determination in step S106 hasbeen performed to be YES, the operation proceeds to step S103 so thatthe ON control signal is output to the power supply circuit 18 to supplyelectric power to each portion.

If a loading/unloading operation is performed during the above-mentionedrepeated operation, the weight in the stoppage state is enlarged orreduced by ΔW or more. Thus, the determination in step S132 is performedto be YES so that the operation proceeds to step S134 so that the HKFflag area 3d is made to be 0. Therefore, the determination in step S123is performed to be YES afterwards so that the operation proceeds tosteps S107 to S116. Then, steps S123 to S126 are performed, and then theoperation returns to step S102. If the weights sequentially calculatedduring the above-mentioned process become different, the difference isadded to the weight which is being displayed to update the displayedweight WD. The above-mentioned operation is repeated at intervals of 10minutes. Since electric power is supplied to each portion in a moment,electric power consumption can be minimized to prevent completeconsumption of the battery. Since electric power is not supplied to thedisplay unit 13 at this time, display is retained to be turned off. Whenthe ignition switch 16 is switched on, an accurate dead weight enlargedor reduced attributable to the loading/unloading operation can bedisplayed on the display unit 13.

As described above, when six seconds or longer have elapsed fromstopping, enlargement or reduction in the weight by the predeterminedweight ΔW or more from the weight in the stoppage state which is thereference weight is detected. In accordance with a result of thedetection, performing of a loading/unloading operation is determined.The enlarged or reduced weights are sequentially added or subtractedwith respect to the weight which is being displayed so as toautomatically update the displayed weight. As a result, the manualoperation means, such as the loading/unloading switch is not required.Thus, a problem in that the weight after loading or unloading cannot bedetected which arises attributable to neglect of the operation can beprevented.

If six seconds have elapsed from stopping, the operation proceeds tostep S132 so that whether or not the absolute value of the differencebetween the contents of the area 3e for weight W1 calculated this timeand those of the area 3h for reference weight WS is equal to thecontents of the area 3i for deviation ΔW or more, that is, whether ornot ΔW≦|W1-W2| is satisfied is determined. This determination isperformed in order to judge whether or not a loading/unloading operationhas been started in accordance with whether or not the weight in thestoppage state has been enlarged or reduced by ΔW or more. However,outputs from sensors have noise, such as vibrations and the likesuperimposed thereon, as shown in FIG. 12. Therefore, the levels of theoutput signals received sequentially at the interval of two secondsscatter. If the levels of the output signals are the maximum value andthe minimum value as shown in FIG. 12, the difference which must be ΔWor more, is made to be ΔW or less. Therefore, the determination in stepS132 cannot accurately be performed.

To overcome the foregoing problem, n (=5) weights detected at intervalsof two seconds are averaged to obtain a mean weight at intervals of 2×nseconds as shown in FIG. 13(a) or a latest weight obtainable atintervals of two seconds is substituted for the most previous weight tomoving-average n weights so as to obtain a mean weight at intervals oftwo seconds as shown in FIG. 13(b).

The pulse interruption routine process shown in FIG. 5 is performed whenthe running pulse signal generated from the running sensor duringrunning of the vehicle is received through the running-sensor signalinput terminal I. When one running pulse is supplied, a determination isperformed that the vehicle is running. Since a running sensor of avehicle sometimes one pulse attributable to rattling generated due torotations even if the vehicle is stopped, a plurality of running pulsesmay be supplied to prevent an error in the operation so as to determinethat the vehicle is being running.

As described above, the weight calculating section 101a calculates theweight in accordance with the signal output from the weight sensor 111,and the display control section 101b causes the weight calculated by theweight calculating section 101a during stoppage to be displayed on thedisplay unit 13. If a determination has been performed that the vehicleis running in accordance with existence of the running pulse signalsupplied from the running sensor mounted on the vehicle, the weightcalculated before running by a predetermined time is displayed on thedisplay unit 13.

Since the weight calculated before running is, as described above,displayed when the vehicle is running, accurate dead weight can bedisplayed even if the dynamic load which is added to the sensorattributable to running of the vehicle is changed. If the vehicle isdetermined to be running, the process for calculating the weight fromthe sensor is interrupted. In this case, the weight calculated beforestoppage, that is, the weight calculated before running by apredetermined time is displayed. Therefore, the load for the processorwhich performs the predetermined process can be reduced.

The display control section 101b causes the display unit 13 to displaythe weight before running for a predetermined time even if the runningvehicle has been stopped. Therefore, if the running vehicle is broughtto the stoppage state, the weight before running is displayed for apredetermined period. Therefore, the load affected by the vibration ofthe vehicle which is in the transition state from running to stopping isnot displayed. Thus, accurate dead weight can be displayed.

The detection section 101c detects start of a loading/unloadingoperation after a predetermined time has elapsed from a moment at whichthe running vehicle has been stopped. The display control section 101bcauses the display unit 13 to display the weight obtained by adding, tothe weight which is being displayed, the difference between the weightssequentially calculated by the weight calculating section 101a in aperiod from detection of the start of the loading/unloading operation bythe detection section 101c to start of running of the vehicle. After apredetermined time has elapsed from a moment at which the runningvehicle has been stopped, start of a loading/unloading operation isdetected. The difference between weights sequentially calculated fromdetection of the start of the loading/unloading operation to start ofrunning of the vehicle is added to the weight which is being displayedso that the obtained weight is displayed. Therefore, the weight enlargedor reduced attributable to the loading/unloading operation is displayed.Even if the place on which the vehicle is stopped during the operationis inclined, accurate weight can be displayed.

When the release detection section 101d has detected brake releasewithin a predetermined time from the moment at which the running vehiclehas been brought to the stoppage state, detection of start of aloading/unloading operation is inhibited for a predetermined time fromdetection of the brake release. If brake release is not detected withina predetermined time from the moment at which the running vehicle hasbeen brought to the stoppage state, detection of start of aloading/unloading operation is enabled after a predetermined time haselapsed from the moment at which the vehicle has been brought to thestoppage state. Therefore, even if the brake is released before thepredetermined time elapses from the moment at which the vehicle has beenbrought to the stoppage state, start of a loading/unloading operation isnot detected for a predetermined time from the brake release. Therefore,the difference between weights sequentially calculated in accordancewith the output signals from the sensors which are changed attributableto the brake release is not added to the weight which is being displayedand the display on the display unit is not updated. Therefore, displayof weight which is performed in accordance with the output signals fromthe sensors which are made to be instable attributable to the brakerelease after the vehicle has been stopped can be prevented. Thus,display of weight to which the accurate weight enlarged or reducedattributable to the loading/unloading operation is reflected can beperformed. Moreover, an overload state can accurately be determined andan alarm can be issued.

The weight calculating section 101a calculates the weight in accordancewith the output signal from the sensor in the first period of thepredetermined time. The display control section 101b determines that thevehicle is running in accordance with the running pulse signal outputfrom the running sensor within the predetermined time. In accordancewith the output signal from the sensor, weight is calculated in thefirst period of the predetermined time. If the vehicle is running withinthe foregoing predetermined time, the weight calculated before runningof the vehicle is displayed. Therefore, even if the load which is addedto the sensor before running of the vehicle is changed, accurate deadweight can be displayed.

Since the detection section 101c detects the operation of the switchwhich is manually operated when a loading/unloading operation is startedto detect start of the loading/unloading operation, weight which isenlarged or reduced by a small quantity attributable to theloading/unloading operation can reliably be displayed.

The detection section 101c detects a fact that the difference betweenthe weight calculated after a predetermined time has elapsed from themoment at which the running vehicle has been stopped and the weightcalculated afterwards has become a predetermined value or more to detectstart of the loading/unloading operation. Therefore, the display ischanged only when the dead weight has been changed attributable to theloading/unloading operation. Thus, accurate dead weight can be displayedso that any manual operation is not required when the operation isstarted. Therefore, the fact that the weight cannot be detected becauseof neglecting of the operation can reliably be prevented.

As described above, according to the invention, weights calculated atpredetermined intervals in accordance with the output signals from thesensors mounted on the vehicle are displayed. Moreover, the differencebetween weights calculated sequentially from detection of start of aloading/unloading operation to start of running of the vehicle is addedto the weight which is being displayed so as to be displayed. Thus,display of weight can be performed such that the weight enlarged orreduced attributable to the loading/unloading operation is reflected tothe weight which is being displayed. Moreover, an overload state can bedetermined and an alarm can be issued. Even if the brake is releasedbefore a predetermined time elapses after a moment at which the vehiclehas been brought to a stoppage state, start of a loading/unloadingoperation is not detected for a predetermined time from the brakerelease. Moreover, the difference between weights calculatedsequentially in accordance with the output signals from the sensorswhich are changed attributable to brake release is not added to theweight which is being displayed and the display on the display unit isnot updated. Therefore, display of weight which is performed inaccordance with the output signals from sensors which have been made tobe instable attributable to the brake release after the vehicle has beenstopped can be prevented. Therefore, display of weight can be performedsuch that the weight enlarged or reduced attributable to theloading/unloading operation is accurately reflected to the weight whichis being displayed. Moreover, an overload state can be determined and analarm can be issued.

What is claimed is:
 1. A dead weight display apparatus comprising:weightcalculating means for calculating a weight at regular intervals inresponse to an output signal from a sensor attached to a vehicle;display means for displaying the weight; display control means forcontrolling said display means to display the weight calculated by saidweight calculating means; detection means for detecting start of aloading/unloading operation; and release detection means for detectingrelease of a brake of the vehicle, wherein said display control meansadds a difference between the weights sequentially calculated by saidweight calculating means from detection of start of theloading/unloading operation performed by said detection means to startof running of the vehicle to the weight which is being displayed andcauses said display means to display the added weight, and wherein atimer counts down a first time period starting when the vehicle stopsmoving, and when said release detection means detects release of thebrake within the first time period, detection of start of aloading/unloading operation which is performed by said detection meansis inhibited for the duration of the first time period, and when saidrelease detection means does not detect release of the brake within thefirst time period, detection of start of a loading/unloading operationwhich is performed by said detection means is enabled after the firsttime period elapses from the stoppage of the vehicle.
 2. The dead weightdisplay apparatus according to claim 1, wherein said release detectionmeans detects release of the brake in accordance with an on/off signalfrom a brake switch.
 3. The dead weight display apparatus according toclaim 1, wherein said display control means controls said display meansto display a weight, which was determined before start of running of thevehicle, for a second time period during running of the vehicle and toretain the display for a third time period after the running vehicle hasbeen brought to a stop.
 4. The dead weight display apparatus accordingto claim 3, wherein said detection means detects a fact that adifference between the weight calculated after detection of start of theloading/unloading operation has been enabled and a weight calculatedpreviously has exceeded a predetermined value to detect start of theloading/unloading operation.